Peptide-based antimicrobials are well-known in the art. They are used in several industries such as personal care products, water treatment, food applications, and medicine and healthcare. For example, in personal care products, antimicrobials are used to help retard or eliminate the growth of topical pathogens as well as to preserve the personal care products from spoiling or to substantially improve the shelf-life of a product. The antimicrobials can also be used to preserve the function of various active ingredients including anti-oxidants (vitamins), emulsifiers, and surfactants.
Previous peptide-based antimicrobials have all been primarily cationic in nature. As a result, they are incompatible with anionic products due to charge interaction. This incompatibility can result in a loss of antimicrobial activity, or in the case of anionic thickeners, a loss of viscosity and clarity.
Thickeners are materials used in the cosmetics industry to increase the viscosity of a product. They play a vital role in maintaining lather quality, delivery of active ingredients (referred to as “actives”) and suspending insoluble ingredients, among others, and are usually used in small quantities (<1%). They are mostly categorized by their origin; the natural polymers have plant, animal or microbial origins, hence their chemical structures are based on proteins or polysaccharides. Examples include Xanthan Gum. The use of those polymers is limited by pH, temperature, solubility and the presence of cations in the system.
The synthetic polymers are acrylic acid-based polymers widely used in small quantities within the cosmetics industry. Acrylic acid polymers are anionic hydrogels capable of swelling but do not dissolve in water. For swelling to occur, the polymers have to be neutralized using a base to form a water soluble salt. Polyacrylic acids are highly sensitive to electrolytes. Examples include carbomers, where base neutralization introduces negatively charged carboxyl groups to the polymer backbone which causes the carbomer to uncoil as a result of the increased repulsive forces. As carbomers are anionic in nature, they are incompatible with cations, creating problems if carbomers must be used in a formulation containing any of the aforementioned excipients, such as cationic antimicrobials. While the application discusses thickeners as an example, it should be appreciated that the application is directed to the compatibility of cationic antimicrobial peptides with anionic compounds as a whole, including, but not limited to, thickeners and surfactants.
Accordingly, there is a clear need for a peptide-based antimicrobial with enhanced activity and cationic-anionic compatibility for use in cosmetics, food, and beverages.